1. Advice to Students from Leaders in the Optics and Photonics Community

  1. Feature Of The Week: In vivo depth-resolved oxygen saturation by dual-wavelength photothermal (DWP) OCT

    All mammalian tissues need oxygen for survival. The human body has a delicately organized vascular network that supplies our tissue with oxygen and other nutrients as well as removing waist products. Not surprisingly, aberrations in vascular oxygen supply are implicated in at least 70 diseases and that number continues to grow. The oxygen distribution from vascular hemoglobin to the parenchymal cells begins with oxygen diffusion first from arterioles with diameters less than 50 µm, and second from capillaries, with deoxygenated blood draining back to venules where the blood is redirected to the lungs for re-oxygenation.

    The earliest abnormalities in oxygen exchange take place at the capillary level and these can often be discerned clinically from hemoglobin oxygen saturation (SaO2) levels in arterioles and venules. Oxygen saturation (SaO2) levels in individual capillaries is frequently too diffuse and requires a great deal of processing and is not easy to interpret, while information from larger (> 50 µm diameter) arteries and veins can be dominated by nearby healthy tissue which mask localized pathology. Conversely, information acquired from target arterioles and venules ranging in diameters from 10-50 µm can provide relatively localized and early signs of oxygen delivery abnormalities that can be valuable for making clinically meaningful conclusions.

    Current approaches to assess microvascular blood oxygenation include: a) invasive approaches such as oxygen-sensitive microelectrode techniques; b) minimally invasive methods with resolution coarser than 50 µm such as phosphorescence quenching imaging of exogenous oxygen sensitive dyes; c) non-invasive without depth resolution such as spectroscopic oximetry; and d) non-invasive with resolution coarser than 50 µm such as functional MRI and photoacoustic imaging.

    Spectroscopic Fourier Domain Optical Coherence Tomography (SFD-OCT) has been reported to measure depth-resolved microvasculature SaO2 levels in phantoms and tissue. However, the variation and complexity of light scattering by blood and tissue limits SaO2 sensitivity of intensity-based SFD-OCT and complicates clinical translation. Recently, our group reported a Dual Wavelength Photothermal (DWP) OCT approach to measure depth-resolved microvasculature SaO2 levels in phantom blood vessels.

    In DWP-OCT, incident photothermal excitation light at two distinct wavelengths is absorbed by target chromophores in a sample resulting in thermally-induced optical pathlength (op) variations that are measured with a phase-sensitive OCT system. Relative concentration of the two target chromophores can be estimated from the normalized ratio of op variations at the photothermal excitation wavelengths. Recently, we extended DWP-OCT to depth-resolved in vivo measurement of SaO2 levels in a 30 µm arteriole in a murine animal model. We believe that DWP OCT instrumentation can provide clinical and biomedical researchers with a powerful tool to improve our understanding of basic pathophysiological processes underlying the natural history of various diseases as well as biomarkers to detect the earliest stages of the disease before irreversible changes have occurred and allow monitoring of long-term progression and effectiveness of selected therapeutic interventions.

    DWP OCT estimation of SaO2 levels relies on measuring optical pathlength (op) that light experiences while traveling from the probe to specific tissue layers and back to the probe. Since op is not influenced by intensity fluctuation as in intensity based spectroscopic methods we believe that further development of DWP OCT will provide an important candidate approach to image microvasculature SaO2 levels for fundamental biomedical research and clinical instrumentation.

    For more information see recent Article. Courtesy Roman V. Kuranov from University of Texas Health Science Center. To share this article click Here.
  2. Recent Articles From Around The Web

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      Explore ekjo.org (5 hours, 40 min ago)

      A Case of Ocular Toxoplasmosis Imaged with Spectral Domain Optical Coherence Tomography A 54-year-old man presented with blurred central vision in the right eye of two weeks' duration. On presentation, visual acuity was 40 / 50 in the right eye and fundus examination showed a whitish-yellow inflammatory lesion near an atrophic, pigmented retinochoroidal scar located in the superotemporal quadrant. Serologic assessment was negative for IgM, but serum IgG to toxoplasma was elevated. Spectral domain optical coherence tomography (SD-OCT) revealed increased reflectivity from the inner retinal layer, retinal thickening, and choroidal shadowing while focal posterior hyaloid thickening and detachment were observed in the new lesion. He was treated with trimethoprim/sulfamethoxazole, clindamycin, and prednisone. ... (Read Full Article)

      Comment Mentions:   Carl Zeiss Meditec   Zeiss Cirrus HD-OCT

    2. High-Resolution Fourier-Domain Optical Coherence Tomography Findings in Subretinal Cysticercosis

      Explore LWW Online (5 hours, 44 min ago)

      High-Resolution Fourier-Domain Optical Coherence Tomography Findings in Subretinal Cysticercosis We preset the optical coherence tomography features of subretinal cysticercosis in a 12-year-old boy with presenting visual acuity of 4/60. (Read Full Article)

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    3. Performance Improvement and Birefringence Investigation of Spectral Domain Optical Coherence Tomography Using a Modified Arrayed Waveguide Grating

      Explore EEMCS EPrints Service (5 hours, 49 min ago)

      Performance Improvement and Birefringence Investigation of Spectral Domain Optical Coherence Tomography Using a Modified Arrayed Waveguide Grating An arrayed-waveguide grating (AWG) with its high accuracy and stability is a powerful tool for spectral analysis. We investigate its potential for spectral-domain optical coherence tomography (SD-OCT). A silicon-oxynitride-based AWG spectrometer for the 800 nm wavelength range is designed for on-chip SD-OCT systems. By removing the output waveguides of the AWG, the depth range is significantly enhanced. In addition, the effect of polarization dependency of the AWG on sensitivity roll-off is investigated and for partial polarization, a beat effect is observed in the depth ranging measurements, which leads to signal fading at specific depths. (Read Full Article)

      Comment Mentions:   University of Twente   Markus Pollnau   Kerstin Wörhoff

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      Explore ekjo.org (5 hours, 54 min ago)

      Retinal Nerve Fiber Layer Measurement Variability with Spectral Domain Optical Coherence Tomography Purpose To evaluate the effect of the scanning laser ophthalmoscope (SLO) guided re-test mode on short- and long-term measurement variability of peripapillary retinal nerve fiber layer (RNFL) thickness obtained by spectral domain-SLO optical coherence tomography (SD-SLO/OCT). Methods Seventy five healthy eyes were scanned 3 times per day (intra-session variability) by both the SLO guided re-test mode and the independent mode of SD-SLO/OCT. Subjects were scanned 3 times by both modes at visits within a 2-week interval (inter-session variability). For testing longitudinal variability, 3 separate exams were performed over 6 months by both modes. The coefficient of variation (CV), reproducibility coefficient ... (Read Full Article)

      Comment Mentions:   University of Ulsan   Ophthalmic Technologies Spectral OCT/SLO   Sung Yong Kang

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      Explore iovs.org (6 hours ago)

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      Comment Mentions:   Seoul National University   UCSD   Robert N. Weinreb

    6. Optical Coherence Tomography of Radiation Optic Neuropathy

      Explore SLACK Journals (6 hours, 28 min ago)

      Optical Coherence Tomography of Radiation Optic Neuropathy BACKGROUND AND OBJECTIVE: To quantitatively study morphologic optic disc and retinal changes in patients with radiation optic neuropathy (RON) using optical coherence tomography (OCT). PATIENTS AND METHODS: This study is a retrospective clinical case series of ten patients with acute RON. Each had been treated with palladium-103 ophthalmic plaque therapy for choroidal melanoma. OCT images were taken at the time of the initial RON diagnosis to measure cup depth, cup width, edema, vasculature diameter, and retinal thickness. RESULTS: All patients with acute RON showed optic disc edema, increased optic disc thickness, and decreased optic cup depth. The average papillary retinal ... (Read Full Article)

      Comment Mentions:   New York Eye and Ear Infirmary

    7. Comparison of Macular Thickness in Diabetic Macular Edema Using Spectral-Domain Optical Coherence Tomography and Time-Domain Optical Coherence Tomography

      Explore Hindawi Publishing Corporation (6 hours, 36 min ago)

      Comparison of Macular Thickness in Diabetic Macular Edema Using Spectral-Domain Optical Coherence Tomography and Time-Domain Optical Coherence Tomography Purpose. To compare the macular thicknesses in diabetic macular edema (DME) measured with spectral-domain optical coherence tomography (SD-OCT) and time-domain (TD) OCT. Patients and Methods. The average macular thicknesses of 50 eyes of 29 patients with DME were measured using SD-OCT and TD-OCT. Results. The mean macular thicknesses measured with TD-OCT and SD-OCT were 4 0 1 . 5 ± 1 1 7 . 8 μm (mean ± SD) and 4 4 6 . 2 ± 1 2 3 . 5 μm, respectively. The macular thicknesses measured with the two devices were well correlated (Pearson's product moment correlation, (Read Full Article)

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    8. Hyperintense plaque identified by magnetic resonance imaging relates to intracoronary thrombus as detected by optical coherence tomography in patients with angina pectoris

      Explore ehjcimaging.oxfordjournals.org (6 hours, 50 min ago)

      Hyperintense plaque identified by magnetic resonance imaging relates to intracoronary thrombus as detected by optical coherence tomography in patients with angina pectoris Aims Many investigators have speculated that hyperintense plaques (HIPs) of the carotid artery on non-contrast T1-weighted imaging (T1WI) in magnetic resonance indicate the presence of mural or intraplaque haemorrhage containing methemoglobin. Coronary plaque imaging with T1WI is challenging, and the clinical significance of coronary HIP on T1WI remains unknown. The aim of this study was to compare HIPs on T1WI with coronary plaque morphology assessed by optical coherence tomography (OCT), which allows us to identify not only plaque rupture, but also fibrous cap thickness and intracoronary thrombus in vivo, in patients with angina pectoris. Methods and results Twenty-six lesions from ... (Read Full Article)

      Comment Mentions:   Lightlab M3 Imaging Console   St. Jude Medical

    9. Diurnal Variation of Choroidal Thickness in Normal, Healthy Subjects Measured by Spectral Domain Optical Coherence Tomography

      Explore iovs.org (7 hours, 14 min ago)

      Diurnal Variation of Choroidal Thickness in Normal, Healthy Subjects Measured by Spectral Domain Optical Coherence Tomography Purpose. To describe the pattern and magnitude of diurnal variation of choroidal thickness (CT), its relation to systemic and ocular factors, and to determine the intervisit reproducibility of diurnal patterns. Methods. A prospective study was conducted on 12 healthy volunteers who each underwent sequential ocular imaging on two separate days at five fixed, 2-hour time intervals. Spectral domain optical coherence tomography (OCT) with enhanced depth imaging and image tracking was performed using a standardized protocol. Choroidal and retinal thicknesses were independently assessed by two masked graders. CT diurnal variation was assessed using repeated-measures ANOVA. Results. A significant diurnal variation in ... (Read Full Article)

      Comment Mentions:   University of Southern California   Srinivas R. Sadda   Yanling Ouyang

    10. Spectral-Domain Optical Coherence Tomography Enhanced Depth Imaging of the Normal and Glaucomatous Nonhuman Primate Optic Nerve Head

      Explore iovs.org (7 hours, 17 min ago)

      Spectral-Domain Optical Coherence Tomography Enhanced Depth Imaging of the Normal and Glaucomatous Nonhuman Primate Optic Nerve Head Purpose. To test whether the enhanced depth imaging (EDI) modality improves anterior and posterior lamina cribrosa surface (ALCS and PLCS) visibility compared with conventional spectral-domain optical coherence tomography (SD-OCT). Methods. Conventional and EDI SD-OCT scans were obtained 30 minutes after IOP was manometrically lowered to 10 mm Hg in both eyes of 14 nonhuman primates (NHPs) with unilateral experimental glaucoma (EG). Thirteen horizontal and seven vertical radial B-scans of each SD-OCT data set were delineated by one operator masked to image type. Delineated ALCS and PLCS points were projected to 1 of 100 equal-sized subregions of the neural canal opening ... (Read Full Article)

      Comment Mentions:   Devers Eye Institute   Brad Fortune   Claude F. Burgoyne

    11. Assessment of Differential Pharmacodynamic Effects using Optical Coherence Tomography in Neovascular Age-Related Macular Degeneration

      Explore iovs.org (7 hours, 22 min ago)

      Assessment of Differential Pharmacodynamic Effects using Optical Coherence Tomography in Neovascular Age-Related Macular Degeneration Purpose: To assess the differential pharmacodynamic effects of bevacizumab (Avastin), pegaptanib (Macugen), and verteporfin photodynamic therapy (PDT), using novel OCT parameters, in a recently completed phase III/IV clinical trial. Methods: Data from 122 patients participating in the Avastin (Bevacizumab) for Choroidal neovascularization (ABC) trial, were evaluated. Stratus OCT images were analyzed using custom software - changes in volume of the neurosensory retina, subretinal fluid (SRF), pigment epithelium detachment (PED), and subretinal tissue, were calculated over the 54-week trial period. Results: Reductions in retinal oedema were more than twice as great from bevacizumab than pegaptanib (-0.82 mm3 versus -0.31 mm3), while ... (Read Full Article)

      Comment Mentions:   University College London   Alexander C. Walsh   University of Southern California

    12. In Vivo Evaluation of Retinal Neurodegeneration in Patients with Multiple Sclerosis

      Explore PLoS ONE (Jan 26 2012)

      In Vivo Evaluation of Retinal Neurodegeneration in Patients with Multiple Sclerosis To evaluate macular morphology in the eyes of patients with multiple sclerosis (MS) with or without optic neuritis (ON) in previous history. Optical coherence tomography (OCT) examination was performed in thirty-nine patients with MS and in thirty-three healthy subjects. The raw macular OCT data were processed using OCTRIMA software. The circumpapillary retinal nerve fiber layer (RNFL) thickness and the weighted mean thickness of the total retina and 6 intraretinal layers were obtained for each (Read Full Article)

      Comment Mentions:   National Institutes of Health   Carl Zeiss Meditec   University of Miami

    13. Catechin prevents severe dyslipidemia-associated changes in wall biomechanics of cerebral arteries in LDLr-/-:hApoB+/+ mice and improves cerebral blood flow

      Explore AJP - Heart and Circulatory Physiology (Jan 26 2012)

      Catechin prevents severe dyslipidemia-associated changes in wall biomechanics of cerebral arteries in LDLr-/-:hApoB+/+ mice and improves cerebral blood flow Endothelial dysfunction and oxidative stress contribute to the atherosclerotic process that includes stiffening of large peripheral arteries. In contrast, we previously reported a paradoxical increase in cerebrovascular compliance in LDLr-/-: hApoB+/+ atherosclerotic (ATX) mice. We hypothesized that prevention of cerebral artery endothelial function with a chronic dietary antioxidant intake would normalize the changes in cerebral artery wall structure and biomechanics and prevent the decline in basal cerebral blood flow (CBF) associated with atherosclerosis. Three-month old ATX mice were treated, or not, for 3 months with the polyphenol (+)-catechin (CAT, 30 mg/kg/day) and compared to wild-type (WT) controls. In isolated pressurized ... (Read Full Article)

      Comment Mentions:   University of Montreal   Ecole Polytechnique de Montréal

    14. Analysis of progression of reticular pseudodrusen by spectral domain optical coherence tomography

      Explore iovs.org (Jan 26 2012)

      Analysis of progression of reticular pseudodrusen by spectral domain optical coherence tomography Purpose: To analyze reticular pseudodrusen progression using SD-OCT. Methods: Thirty-three consecutive patients (48 eyes) underwent Spectralis SD-OCT using the eye-tracked follow-up protocol 24+/-2 months after baseline examination. Each pair of B-scans (only 1 per eye was evaluated among those showing pseudodrusen progression) was compared with respect to pseudodrusen appearance and retinal layers structure. Stage 1 pseudodrusen was defined as granular material between the RPE and the IS/OS, stage 2 as mounds of material sufficient to alter the contour of the IS/OS, stage 3 as thicker material adopting a conical appearance and breaking through the IS/OS, and stage 4 as fading ... (Read Full Article)

      Comment Mentions:   Heidelberg Spectralis   Centre Hospitalier Intercommunal de Créteil   Eric H. Souied

    15. The physiological variation of the retinal nerve fibre layer thickness and macular volume in humans as assessed by spectral-domain optical coherence tomography

      Explore iovs.org (Jan 26 2012)

      The physiological variation of the retinal nerve fibre layer thickness and macular volume in humans as assessed by spectral-domain optical coherence tomography Purpose With the introduction of spectral domain optical coherence tomography (SD-OCT), changes in the retinal nerve fibre layer (RNFL) thickness and macular volume (MV) can be detected with a high precision. This study aimed to determine whether there is a physiological quantifiable degree of variation of these structures in humans. Methods This study took place during a 10 km charity run at VU University Amsterdam. Weight, height, hydration status, RNFL thickness (ring scan,12 degrees around the optic nerve head) and MV (20x20 degrees) were assessed in all 69 subjects (44 runners, 25 controls) using the Heidelberg Spectralis with eye-tracking function. ... (Read Full Article)

      Comment Mentions:   University College London   Heidelberg Spectralis   VU University Amsterdam